Generate Built-Using at the build time

Closes: #831271

3 files changed, 106 insertions, 18 deletions

diff --git a/debian/control b/debian/control
index f1ba060..8ce9f4c 100644
--- a/debian/control
+++ b/debian/control
@@ -19,6 +19,7 @@ Build-Depends: debhelper (>= 11),
                python3-certifi,
                python3-chardet,
                python3-colorama,
+               python3-debian,
                python3-distlib,
                python3-distro,
                python3-html5lib,
@@ -80,24 +81,26 @@ Package: python-pip-whl
 Architecture: all
 Depends: ca-certificates,
          ${misc:Depends},
-Built-Using: chardet (= 2.3.0-2),
-             distlib (= 0.2.4-1),
-             html5lib (= 0.999999999-1),
-             pyparsing (= 2.1.10+dfsg1-1),
-             appdirs (= 1.4.0-2),
-             python-cachecontrol (= 0.11.7-1),
-             python-colorama (= 0.3.7-1),
-             python-distro (= 1.0.1-1),
-             python-ipaddress (= 1.0.17-1),
-             python-lockfile (= 1:0.12.2-2),
-             python-packaging (= 16.7-2),
-             python-progress (= 1.2-1),
-             python-retrying (= 1.3.3-1),
-             python-setuptools (= 32.3.1-1),
-             python-urllib3 (= 1.16-1),
-             python-webencodings (= 0.5-1),
-             requests (= 2.11.1-1),
-             six (= 1.10.0-3),
+Built-Using: ${pip:Built-Using}
+X-Built-Using:
+             chardet,
+             distlib,
+             html5lib,
+             pyparsing,
+             appdirs,
+             python-cachecontrol,
+             python-colorama,
+             python-distro,
+             python-ipaddress,
+             python-lockfile,
+             python-packaging,
+             python-progress,
+             python-retrying,
+             python-setuptools,
+             python-urllib3,
+             python-webencodings,
+             requests,
+             six,
 Breaks: python-chardet-whl (<< 2.3.0-2),
         python-colorama-whl (<< 0.3.6-1),
         python-distlib-whl (<< 0.2.2-1),
diff --git a/debian/genbuildusing.py b/debian/genbuildusing.py
new file mode 100755
index 0000000..a082b58
--- /dev/null
+++ b/debian/genbuildusing.py
@@ -0,0 +1,84 @@
+#!/usr/bin/python3
+import os
+import sys
+import gzip
+from debian.deb822 import Deb822, PkgRelation, _PkgRelationMixin
+from debian.changelog import Changelog
+
+class Control(Deb822, _PkgRelationMixin):
+    """
+    This class automatically parses relationship fields.
+    """
+    _relationship_fields = [
+        'build-depends',
+        'x-built-using',
+        'built-using',
+        'depends',
+        'pre-depends',
+        'recommends',
+        'suggests',
+        'breaks',
+        'conflicts',
+        'provides',
+        'replaces',
+        'enhances',
+    ]
+
+    def __init__(self, *args, **kwargs):
+        # type: (*Any, **Any) -> None
+        Deb822.__init__(self, *args, **kwargs)
+        _PkgRelationMixin.__init__(self, *args, **kwargs)
+
+source_pkg = None
+wheel_pkg = None
+
+# We cannot put unversioned source package names in Built-Using
+# since dpkg-gencontrol doesn’t allow overriding them with
+# versioned package names (unlike in, say, Depends), making
+# that non-trivial to substitute.
+# 
+# Instead, we put them into X-Built-Using, which also prevents
+# them from leaking into the binary package’s control file.
+
+for pkg in Control.iter_paragraphs(open('debian/control')):
+    if 'Source' in pkg:
+        source_pkg = pkg
+    if 'X-Built-Using' in pkg:
+        wheel_pkg = pkg
+
+if not source_pkg and not wheel_pkg:
+    print('no source packages or packages with Built-Using found', file=sys.stderr)
+    exit(1)
+
+if len(sys.argv) < 2:
+    print('substvars file required', file=sys.stderr)
+    exit(1)
+
+substvars_file = sys.argv[1]
+
+def nowarn(*args):
+    pass
+
+# To prevent the parser from complaining about substitutions
+import warnings
+warnings.warn = nowarn
+
+# if len(...) is needed to allow the trailing comma
+# this doesn’t allow alternative built-dependencies
+build_depends = [x[0]['name'] for x in source_pkg.relations['build-depends'] if len(x[0]['name'])]
+# this also filters out substitutions — no longer needed since we need X-Built-Using anyway :(
+built_using = [x[0]['name'] for x in wheel_pkg.relations['x-built-using'] if not x[0]['name'].startswith('${')]
+
+def get_source_and_version(pkg):
+    # try non-native location first
+    changelog_path = os.path.join('/usr/share/doc', pkg, 'changelog.Debian.gz')
+    if not os.path.exists(changelog_path):
+        changelog_path = os.path.join('/usr/share/doc', pkg, 'changelog.gz')
+    changelog = Changelog(file=gzip.open(changelog_path, 'rb'))
+    return changelog.get_package(), changelog.get_version()
+
+build_depends_sources = [get_source_and_version(x) for x in build_depends]
+
+built_using_versions = [[{'name': pkg, 'version': ('=', str(ver))}] for (pkg, ver) in build_depends_sources if pkg in built_using]
+
+print('pip:Built-Using=%s' % PkgRelation.str(built_using_versions), file=open(substvars_file, 'a'))
diff --git a/debian/rules b/debian/rules
index 512996d..ae5e15d 100755
--- a/debian/rules
+++ b/debian/rules
@@ -71,6 +71,7 @@ override_dh_auto_install:
 	python3 setup.py bdist_wheel \
 		--universal \
 		-d $(CURDIR)/debian/python-pip-whl/usr/share/python-wheels
+	debian/genbuildusing.py debian/python-pip-whl.substvars
 
 override_dh_installchangelogs:
 	dh_installchangelogs NEWS.rst